// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_DNS_DNS_CONFIG_SERVICE_WIN_H_
#define NET_DNS_DNS_CONFIG_SERVICE_WIN_H_

// The sole purpose of dns_config_service_win.h is for unittests so we just
// include these headers here.
#include <iphlpapi.h>
#include <winsock2.h>

#include <memory>
#include <string>
#include <vector>

#include "base/macros.h"
#include "base/memory/free_deleter.h"
#include "base/memory/ref_counted.h"
#include "base/strings/string16.h"
#include "net/base/net_export.h"
#include "net/dns/dns_config_service.h"

// The general effort of DnsConfigServiceWin is to configure |nameservers| and
// |search| in DnsConfig. The settings are stored in the Windows registry, but
// to simplify the task we use the IP Helper API wherever possible. That API
// yields the complete and ordered |nameservers|, but to determine |search| we
// need to use the registry. On Windows 7, WMI does return the correct |search|
// but on earlier versions it is insufficient.
//
// Experimental evaluation of Windows behavior suggests that domain parsing is
// naive. Domain suffixes in |search| are not validated until they are appended
// to the resolved name. We attempt to replicate this behavior.

namespace net {

namespace internal {

    // Parses |value| as search list (comma-delimited list of domain names) from
    // a registry key and stores it in |out|. Returns true on success. Empty
    // entries (e.g., "chromium.org,,org") terminate the list. Non-ascii hostnames
    // are converted to punycode.
    bool NET_EXPORT_PRIVATE ParseSearchList(const base::string16& value,
        std::vector<std::string>* out);

    // All relevant settings read from registry and IP Helper. This isolates our
    // logic from system calls and is exposed for unit tests. Keep it an aggregate
    // struct for easy initialization.
    struct NET_EXPORT_PRIVATE DnsSystemSettings {
        // The |set| flag distinguishes between empty and unset values.
        struct RegString {
            bool set;
            base::string16 value;
        };

        struct RegDword {
            bool set;
            DWORD value;
        };

        struct DevolutionSetting {
            // UseDomainNameDevolution
            RegDword enabled;
            // DomainNameDevolutionLevel
            RegDword level;
        };

        DnsSystemSettings();
        ~DnsSystemSettings();

        // Filled in by GetAdapterAddresses. Note that the alternative
        // GetNetworkParams does not include IPv6 addresses.
        std::unique_ptr<IP_ADAPTER_ADDRESSES, base::FreeDeleter> addresses;

        // SOFTWARE\Policies\Microsoft\Windows NT\DNSClient\SearchList
        RegString policy_search_list;
        // SYSTEM\CurrentControlSet\Tcpip\Parameters\SearchList
        RegString tcpip_search_list;
        // SYSTEM\CurrentControlSet\Tcpip\Parameters\Domain
        RegString tcpip_domain;
        // SOFTWARE\Policies\Microsoft\System\DNSClient\PrimaryDnsSuffix
        RegString primary_dns_suffix;

        // SOFTWARE\Policies\Microsoft\Windows NT\DNSClient
        DevolutionSetting policy_devolution;
        // SYSTEM\CurrentControlSet\Dnscache\Parameters
        DevolutionSetting dnscache_devolution;
        // SYSTEM\CurrentControlSet\Tcpip\Parameters
        DevolutionSetting tcpip_devolution;

        // SOFTWARE\Policies\Microsoft\Windows NT\DNSClient\AppendToMultiLabelName
        RegDword append_to_multi_label_name;

        // True when the Name Resolution Policy Table (NRPT) has at least one rule:
        // SOFTWARE\Policies\Microsoft\Windows NT\DNSClient\DnsPolicyConfig\Rule*
        bool have_name_resolution_policy;
    };

    enum ConfigParseWinResult {
        CONFIG_PARSE_WIN_OK = 0,
        CONFIG_PARSE_WIN_READ_IPHELPER,
        CONFIG_PARSE_WIN_READ_POLICY_SEARCHLIST,
        CONFIG_PARSE_WIN_READ_TCPIP_SEARCHLIST,
        CONFIG_PARSE_WIN_READ_DOMAIN,
        CONFIG_PARSE_WIN_READ_POLICY_DEVOLUTION,
        CONFIG_PARSE_WIN_READ_DNSCACHE_DEVOLUTION,
        CONFIG_PARSE_WIN_READ_TCPIP_DEVOLUTION,
        CONFIG_PARSE_WIN_READ_APPEND_MULTILABEL,
        CONFIG_PARSE_WIN_READ_PRIMARY_SUFFIX,
        CONFIG_PARSE_WIN_BAD_ADDRESS,
        CONFIG_PARSE_WIN_NO_NAMESERVERS,
        CONFIG_PARSE_WIN_UNHANDLED_OPTIONS,
        CONFIG_PARSE_WIN_MAX // Bounding values for enumeration.
    };

    // Fills in |dns_config| from |settings|. Exposed for tests.
    ConfigParseWinResult NET_EXPORT_PRIVATE ConvertSettingsToDnsConfig(
        const DnsSystemSettings& settings,
        DnsConfig* dns_config);

    // Use DnsConfigService::CreateSystemService to use it outside of tests.
    class NET_EXPORT_PRIVATE DnsConfigServiceWin : public DnsConfigService {
    public:
        DnsConfigServiceWin();
        ~DnsConfigServiceWin() override;

    private:
        class Watcher;
        class ConfigReader;
        class HostsReader;

        // DnsConfigService:
        void ReadNow() override;
        bool StartWatching() override;

        void OnConfigChanged(bool succeeded);
        void OnHostsChanged(bool succeeded);

        std::unique_ptr<Watcher> watcher_;
        scoped_refptr<ConfigReader> config_reader_;
        scoped_refptr<HostsReader> hosts_reader_;

        DISALLOW_COPY_AND_ASSIGN(DnsConfigServiceWin);
    };

} // namespace internal

} // namespace net

#endif // NET_DNS_DNS_CONFIG_SERVICE_WIN_H_
